Method of surfacing roadways



Patented Apr. 17, 1934 PATENT OFFICE METHOD OF SURFACING ROADWAYS LeonR. MacKenzie, Des Moines, Iowa, assignor to L. R. MacKcnzieIncorporated, Tulsa, Okla., a corporation of Delaware No Drawing.Application August 19, 1931, Serial No. 558,103

3 Claims.

The purpose of the present invention is to provide a simple and veryeconomical method for surfacing roadways to render them waterproof, toincrease their stability and to make them dustless.

In accomplishing these purposes, I preferably precoat the material ofthe roadway surface, after suitable preparation with a highly volatilefluid, acid or non-acid as desired, and apply to the surface of the roadcold bituminous emulsion to which there may or may not have been added,subsequent to emulsification, a neutral or alkaline highly volatilefluid. I have found that a bituminous emulsion to which has been addednon-acid highly volatile fluid is to be preferred in many instances.

The nature of the highly volatile fluid is such that when the steps ofmy process are properly followed, the pre-coating of the mineral surfacematerial of the road with such fluid facilitates the rapid spread of thebituminous emulsion, serves as a partial temporary flux for the bitumen,then contributes to the setting of the bitumen on the road material andaccelerates the hardening of the bitumen.

I am aware of the fact that previous applications have used oils for thepre-coating of mineral particles but in all such applications known tome, these oils are complete solvents of bitumen, having a low degree ofvolatility which prevents rapid evaporation and thus retards instead ofaccelerates the hardening action of the bitumen applied, and such oilsare therefore not adapted for the purposes of this invention.

With these general objects in'view, the invention of my presentapplication consists of the method whereby these objects are attained ashereinafter more fully explained.

In some sections of the country there are many miles of highway that arepeculiarly adapted for the practice of the method. Efforts have beenmade to use asphalt treatments for such highways, but these efforts havebeen only relatively successful and in only a few localities due topeculiar soil conditions.

Treatments of crude oil well worked into the earth or gravel surfaceshave also been used with fair success, but oil treatments have thedecided disadvantage that they are detrimental to rubber tires and thatin a relatively short time the crude oil loses its volatile constituentsand there is left a rather sticky mass which is very detri mental topaint on vehicles when deposited on them, and after the crude oil hasstood for some time longer the roads again become dusty, and

the oil treated dust from such roads is particularly obnoxious anddetrimental to traffic.

Such treatments of this kind as have been most successful have requiredrepeated applications, the cost of which finally approaches too closelyto the cost of a high type improvement to be sound expenditureeconomically.

I will now illustrate how my method would be applied to the surfacing ofa road of the character mentioned.

The road surface material is first loosened by scarifying or any otherdesirable method to any desired depth. It is then pulverized byharrowing or otherwise. The surface is then permitted to dry thoroughly.In case time or weather conditions are such that drying cannot beproperly clone, artificial drying of some sort may be practiced, as forexample by running a heating machine over the loosened surface.

Under certain conditions it may be necessary where moisture cannot beremoved from the loosened particles to treat them with a dilute acid oralkaline solution, the purpose of which will more fully appear below.

The loosened surface is then preferably given a coat of highly volatilefluid, such for instance as certain grades of gasoline, benzol, naptha,carbon-tetrachloride, or alcohol or the like. This may be sprayed,sprinkled or otherwise applied and thereupon the surface is preferablyimmediately harrowed'or otherwise agitated so as to assist the highlyvolatile fluid to penetrate quickly to the depth of the loosened part ofthe surface and as nearly as possible to coat all the loose particles.

As promptly thereafter as possible, and in any event before substantialevaporation of the high- 1y volatile fiuid,I deposit on the road surfacea cold bituminous emulsion which likewise may be sprinkled or sprayed orotherwise deposited on the road and immediately thereafter theharrowing, blading or an equivalent operation should be repeated forassisting the bituminous emulsion to penetrate and coat all of theloosened particles.

The mechanical mixing in place, is not an essential operation in allcases but will expedite the penetration of the mass and the coating ofthe individual particles. It will also greatly assist in securing a goodriding surface. The highly volatile fluid even without the mechanicalmixing will facilitate the rapidity of the spread of the bituminousemulsion by causing it to form into a thin film or coating on theloosened particles of the road surface and cause quick and permanentadherence of the bitumen to the particles.

On account of the fact that the loose particles have been pre-coatedwith the highly volatile fluid I find that certain results can beobtained with the bituminous emulsion that would not otherwise bepossible.

By way of illustration, if there is a layer of dry dust in a wheel rutand bituminous emulsion is poured into the dust without suchpre-coating,it will not penetrate the layer of dust at all. If, on the other hand,the same dust is pre-coated with a highly volatile fluid of the kindmentioned above and the bituminous emulsion is then poured into the rut,the emulsion will immediately spread throughout the layer of dust andthinly coat each particle of dust.

The use of a highly volatile fluid also promotes adherence of thebitumen content of the emulsion to the particles, and the highlyvolatile fluid acts as a partial and temporary flux.

Since moisture, if any, in the road surface particles has already beenrendered acid by appropriate treatment, and since the highly volatilefluid is also usually slightly acid, or can be readily'rendered slightlyacid, whereas the bituminous emulsion is always slightly alkaline, itfollows that acid acting upon the alkaline bituminous emulsion causesthe emulsion to break down and causes the bitumen to separate from theliquefier content of the emulsion and remain deposited upon theparticles of the road surface in thin films.

Bituminous emulsion always has a specific degree of alkalinity at whichit is most stable. By rendering the mass strongly alkaline, considerablybeyond the degree of alkalinity necessary to retain the bitumen in anemulsified form, I am able to produce the same result whereby theemulsion is caused to break down and the bitumen to be deposited uponthe particles.

The evaporation of the highly volatile fluid then greatly facilitatesthe evaporation of the liquefler leaving the bitumen as originallyspread in the emulsified form in a condition to harden rapidly. Propertime should be permitted to elapse for the hardening of the bitumen andthereafter the loose surface particles should be compacted. Thecompacting is preferably done with a roller, but may in some instancesbe left to. the action of trafiic.

A road surface made in this way will be waterproof for all practicalpurposes so that surface water will flow off. There will be formed asubstantial surface coat which will maintain the stability of the roadboth on account of the waterproof nature of this coat and because itserves to hold the particles together. It is also true that the coatingwould largely prevent trafiic from displacing any under layer of earth,gravel or the like. Aroad surface constructed in this way originates nodust.

In event of later excessive traffic, by adding another thin surfacecoating before the original has been broken up, and continuing to so addlayers from time to time as needed, it is possible to build up a thickdurable hard surfaced road.

It is, of course, obvious that the nature of different kinds of soils,loams, gravels, clays and so on will require different relative amountsof highly volatile fluid and bituminous emulsion. The viscosity of theemulsion may be varied for different road materials, if necessary ordesired.

In addition to the advantages already mentioned, attention is called tothe ease and simplicity with which the method may be practiced.

Light traffic graveled roads may be changed into roads with densewaterproof surfaces with a minimum of trouble and cost. On account ofthe economy of this method, many roads which otherwise could not besurfaced on account of the expense, may be provided with satisfactorysurfaces.

Any surplus of highly volatile fluid will penetrate the hard surfaceunder the separated and treated particles, and will help the bonding ofthe bituminous coated particles with the base and it is often desirableto use a surplus for this purpose. A surplus of emulsion will penetratesomewhat into the base and thus form a bond.

Beneficial results to the mass of particles constituting the roadsurface may be obtained at times by omitting the step of pre-coating thematerial with a highly volatile fluid and instead applying, after thematerial has been suitably prepared a bituminous emulsion to which hasbeen added a suitable highly volatile fluid. The highly volatile fluidwhich is added to the emulsion should be non-acid in character, eitheralkaline or neutral. The beneficial results obtained in this way may begreatly enhanced by immediate thorough agitation of the mass after theapplication of the emulsion has been made.

At other times the step of pre-coating the particles with highlyvolatile fluid (either alkaline, acid-or neutral) may be followed by anapplication of a liqueous bituminous emulsion to which, has been added anon-acid highly volatile fluid. In this way quicker results may beobtained as to penetration and spread of the bitumen, particularly whenfollowed by immediate thorough agitation.

From the foregoing, it is obvious that the use of oils as brought out byprevious applications will not accomplish the results obtained throughmy process in which I use a highly volatile fluid for the precoating ofmineral particles.

I claim as my invention:

1. A method of preparing a roadway comprising loosening and pulverizingthe upper surface, applying to the finely divided resulting particles acoating of highly volatile fluid, then before evaporation of such fluidcoating has substantially progressed, pouring upon the particlesbituminous emulsion, agitating the particles and emulsion to causecoating of the particles by the emulsion and to insure that the coatedmaterials shall be in a loosened state for aeration, allowing theloosened mass to lie and aerate and the emulsion to break and thencompacting the mass.

2. A method of treating a roadway having an upper surface of finelydivided loosened material, comprising applying to the finely dividedparticles a coating of highly volatile fluid, then before evaporation ofsuch fluid coating has substantially progressed, pouring upon theparticles bituminous emulsion, agitating the particles and emulsion forinsuring the thorough coating of the particles by the emulsion and forinsuring that the coated material shall be in a loosened state foraeration, allowing the loosened mass to lie and aerate and the emulsionto break and then compacting the mass.

3. A method of preparing a roadway having an upper surface of finelydivided loosened material, comprising applying to the finely dividedparticles a coating of highly volatile fluid, then before evaporation ofsuch fluid coating has substantially progressed, pouring upon theparticles bituminous emulsion in an amount sufficient to provide aslight excess over the amount required 1.

loosened state for aeration, allowing the excess of the emulsion topenetrate downward to and into the undisturbed portion of the roadway,and allowing the loosened mass to lie and aerate and the emulsion tobreak, and then compacting the mass.

LEON R. MACKENZIE.

